08-03-23 - U and Es Flashcards
Learning outcomes
- Awareness of the theory of fluid and electrolyte balance.
- Understanding of the concepts of volumes, compartments, content, concentration and input/output.
- Appreciation that fluid and electrolyte balance is central to the provision of appropriate acute clinical care
What substances are measured when looking at fluid and electrolytes in Fife?
What 2 other values can be calculated?
What do U and E measurements allow clinicians to do?
- Substances are measured when looking at fluid and electrolytes in Fife:
1) Na, K, Creatinine
* Fitted as standard
2) + Urea
* For hospital patients on request by GP’s
3) Cl-
* Available freely on request
4) Bicarbonate
* Available on request hospital patients, too unstable for out-patient requesting
- 2 other values can be calculated:
1) eGFR
2) AKI flags. - U and E measurements allow clinician to make a broad estimate of water status.
What are 3 relates systems/hormones to Us and Es?
- 3 related systems/hormones to Us and Es:
1) Anti-diuretic hormone
2) Renin-angiotensin system
3) Aldosterone
What are 3 cases in which abnormal electrolytes can be present?
What 4 processes are electrolytes important for?
- 3 cases in which abnormal electrolytes can be present:
1) Primary disease state
2) Secondary consequence of a multitude of diseases
5) Iatrogenic problems are very common
* Relating to illness caused by medical examination or treatment.
- 4 processes electrolytes are important for:
1) Maintenance of cellular homeostasis
2) Cardiovascular physiology - BP
3) Renal physiology - GFR
4) Electrophysiology - heart, CNS
What are the normal ECF and ICF concentrations/volumes for water Na+ and K+ (in picture)?
What are 6 clinical scenarios where electrolytes can become deranged?
- 6 clinical scenarios where electrolytes can become deranged:
1) Haemorrhage - accidents, surgery
2) D&V
3) Poor intake - elderly
4) Increased losses - pyrexia, heat
5) Diuretic therapy
6) Endocrine disorders - Diabetes insipidus, Diabetes mellitus, disorders of ADH, aldosterone etc.
What are 3 compensatory mechanisms for deranged electrolytes?
What are 3 therapeutic interventions for deranged electrolytes?
- 3 compensatory mechanisms for deranged electrolytes:
1) Thirst
2) ADH (anti-diuretic hormone)
3) Renin / Angiotensin system - 3 therapeutic interventions for deranged electrolytes:
1) Intravenous therapy
2) Diuretics
3) Dialysis
In what state does the body fluid system normally exist in?
What can change in a factor cause?
- Normally the body fluid system is maintained in equilibrium
- Changing any factor causes a new steady state to be reached
In what clinical scenarios could be lose 2L of isotonic fluid?
How does this affect the body fluid system?
- We could lose 2L of isotonic fluid from blood or fistula fluid
- There is:
1) Loss is from ECF
2) No change in [Na]
3) No fluid redistribution
What happens if we replace the 2L loss of isotonic fluid with isotonic fluid or hypotonic fluid?
- If we replace the 2L loss of isotonic fluid with isotonic fluid:
1) No change in [Na]
2) No fluid redistribution - If we replace the 2L loss of isotonic fluid with isotonic fluid:
1) Fall in [Na]
2) Fluid redistribution
Where could we lose 3L of hypotonic fluid from?
How does this affect the body fluid system?
- We could lose 3L of hypotonic fluid from insensible loss
- Insensible fluid loss is the amount of body fluid lost daily that is not easily measured, from the respiratory system, skin, and water in the excreted stool
- This leads to:
1) Greater loss from ICF than ECF
2) Small increase in [Na]
3) Fluid redistribution between ECF & ICF
When is ADH release stimulated?
What 2 changes does ADH release leads to?
How do we measure ADH?
- ADH release is stimulated in response to a rise in concentration of osmotically active particles (increase in osmolality, particularly in sodium - It is actually osmolarity which is measured, but universally known and reported as osmolality)
- 2 changes ADH release leads to:
1) Decreased renal water loss
2) Increases thirst - ADH analysis is not readily available – assess status by:
1) Measuring plasma & urine osmolality
2) Urine > plasma suggests ADH is active
RAAS.
When is renin released?
In what 2 situations can IVV decrease?
What is the role of aldosterone?
How can we assess RAAS status?
- RAAS
- Renin release is activated by reduced intra-vascular volume (IVV)
- 2 situations IVV can decrease:
1) Na depletion
2) Haemorrhage - Aldosterone induces renal Na retention
- Simple test to ascertain RAAS status:
- Measure plasma & urine Na
- If urine < 10 mmol/L suggests R/A/A active
Why are urine reference intervals difficult to establish?
What should we be concerned with?
What is a rough concentration for urine (in picture):
* Sodium
* Potassium
* Urea
* Osmolality
* Creatinine
- Reference intervals for urine are difficult to establish as the kidney has an enormous capacity to save & excrete analytes as required – The concentration of the urine will affect the concentration of different substances it contains
- Therefore, we are most concerned with what is appropriate for the blood results and clinical situation e.g. if blood Na+ is normal, we wont be concerned about the Na+ urine concentration
What is urea is a breakdown product of?
Where is it filtered?
What volume enters the tubular lumen per day?
How much of this is urea?
- Urea is a normal breakdown product of protein
- It is filtered at the glomerulus & a major component of urine.
- ~200L plasma ultrafiltrate enters tubular lumen per day
- This represents typically 800 mmol (48g) of urea.